id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
36449	Mismatched fields in composite primary key ForeignObject example model	Jacob Walls	Jacob Walls	"The field types on [https://docs.djangoproject.com/en/5.2/topics/composite-primary-key/#composite-primary-keys-and-relations this example model] are not correct; the primary key of `Order` is CharField, and `Product` is IntegerField:

{{{#!py
class Foo(models.Model):
    item_order_id = models.IntegerField()
    item_product_id = models.CharField(max_length=20)
    item = models.ForeignObject(
        OrderLineItem,
        on_delete=models.CASCADE,
        from_fields=(""item_order_id"", ""item_product_id""),
        to_fields=(""order_id"", ""product_id""),
    )
}}}

It should be:
{{{#!py
class Foo(models.Model):
    item_order_id = models.CharField(max_length=20)
    item_product_id = models.IntegerField()
    item = models.ForeignObject(
        OrderLineItem,
        on_delete=models.CASCADE,
        from_fields=(""item_order_id"", ""item_product_id""),
        to_fields=(""order_id"", ""product_id""),
    )
}}}

Found this while trying to write a test with these models, e.g. this fails:

{{{#!py
In [28]: f = Foo.objects.first()

In [29]: f.item
Out[29]: <OrderLineItem: OrderLineItem object ((1, '1'))>

In [30]: Foo.objects.filter(item=item)
Out[30]: ---------------------------------------------------------------------------
UndefinedFunction                         Traceback (most recent call last)
File ~/django/django/db/backends/utils.py:105, in CursorWrapper._execute(self, sql, params, *ignored_wrapper_args)
    104 else:
--> 105     return self.cursor.execute(sql, params)

UndefinedFunction: operator does not exist: character varying = integer
LINE 1: ....""item_order_id"", ""models_foo"".""item_product_id"") = ('1', 1)...
                                                             ^
HINT:  No operator matches the given name and argument types. You might need to add explicit type casts.
}}}


----
While here, also suggest documenting inside the caveats about how `ForeignObject` differs from `ForeignKey` that the `on_delete` argument is ignored."	Bug	closed	Documentation	5.2	Normal	fixed			Ready for checkin	1	0	0	0	1	0